An electrode for a fuel cell is equipped with a gas diffusion layer (GDL) and a catalyst layer. The gas diffusion layer generally uses a porous material to smoothly supply the catalyst later with fuel or oxidant. Exemplary of the commonly used porous materials include carbon paper, carbon cloth, and carbon felt.
However, these materials have the disadvantage of breaking easily due to their low strength and are generally unable to endure the pressure added during the hot-pressing process necessarily required to fabricate a fuel cell. In addition, they tend to lower the output voltage of a fuel cell because they cannot maintain appropriate humidity of a membrane-electrode assembly due to the low hygroscopic capability. Accordingly, a method to improve these disadvantages has been attempted by setting separate humidifying equipment into a cell to maintain a predetermined hygroscopicity, but this method tends to raise the manufacturing cost and further complicates the fabrication procedures.
Another recent attempt has involved arranging a micro-porous layer (MPL) on the interface of the gas diffusion layer (GDL) adjoining the catalyst layer to maintain a predetermined hygroscopicity, but that approach has also failed to overcome the above disadvantages, while complicating fabrication procedures and raising the manufacturing cost.